Azaleas can be a bit tricky to grow. I know I have received my fair share of azalea related questions of my years here at Bob's. This week I turned to The United States National Arboretum website where they have a definitive guide to all things azalea. Did you know that azaleas belong to the genus Rhododendron? Here are some common azalea questions:

I planted a new azalea and it died. What did I do wrong?

It may have simply dried out. If you plant azaleas in late spring, it is very important to give them some extra water while they are growing new roots. Never let the soil completely dry out it's best to keep the soil evenly moist. Too much water or poorly drained soil might be another explanation of sudden azalea death. Azaleas have very fine, fibrous roots that are easily damaged by waterlogging, even for short periods of time. Before you plant your azalea, dig a hole and fill it with water. If the water has not drained out of the hole within one hour, the soil is poorly drained and you must correct the drainage problem before planting. Install a perforated pipe or drain tile in the garden, making sure that the outlet is lower than the bottom of the planting hole, or build raised beds.

Can you tell me how to plant an azalea?

Plant your azalea in early spring or early fall. If your soil is loose, well drained, and has lots of organic matter, planting will be easy. If drainage is poor, you'll need to correct the drainage problem or plant in raised beds. You can work in some well-rotted leaf mold or compost if the soil is short of organic matter. Don't worry about preparing the soil deeply since azalea roots are shallow and most are found in the top foot of soil. Instead, loosen the soil in a broad area around the planting site. If a soil test reveals that your soil is strongly alkaline, work in enough iron sulfate or ammonium sulfate to drop the pH to 4.5 to 5.5; your state's soil testing lab can give you guidance on how much of these materials are needed to acidify your soil. Water the pot thoroughly before planting and tease the soil away from the roots on the outside of the pot. Don't worry about injuring the roots it's more important to remove a significant amount of the potting soil than it is to keep every root intact. Plant the azalea slightly higher than the surrounding soil since it will probably settle after planting. Finally, water the whole area thoroughly and apply a thin layer of shredded leaves, pine needles, or pine bark to keep the soil cool and moist. Water your newly planted azalea weekly if the weather is dry, at least for the first year.

An old, established azalea died in my garden. What might have caused its death?

There are several possibilities. Voles, also known as meadow mice, may have chewed on the bark and roots near the crown of the plant. Sometimes they chew all the way around the trunk and kill the inner bark, resulting in death of the whole plant. Keep mulch away from the trunk to discourage voles. The bark may also split when there are wide fluctuations in temperature in the winter. Azaleas may begin to come out of dormancy if late winter weather is warm; if a cold snap follows, bark injury is likely, especially in sunny, exposed sites. Prolonged drought weakens plants and often results in the appearance of fungal cankers on the branches of older azaleas. Look for branches that wilt in hot, dry weather in late summer and be sure to water azaleas if drought drags on more than a few weeks. Prune out the affected branches to stop the spread of fungal canker diseases.

What should I use to mulch my azaleas? Should I amend the soil at the time of planting?

You can mulch azaleas with shredded leaves, leaf mold, pine needles, or pine bark mulch. Don't use shredded hardwood mulch since it often drives the pH upward. Pine bark is especially useful since it can lower the pH where it is too high, but it is best used on relatively flat ground since it's light in weight and tends to float away in heavy rain.

You only need to amend the soil if it is devoid of organic matter or if the pH is too high. Have a soil test done by your local extension service to determine if something needs to be added. A light amount of well-decayed organic matter dug into the top layer of soil is helpful for retaining moisture and preventing compaction.

How and when should I prune my azaleas?

Prune azaleas just after they have finished flowering. Remove individual branches back to the spot where they join a larger branch. New flower buds for next spring's bloom are set by midsummer, and any pruning after mid-June could result in diminished flower production next year. Avoid shearing azaleas since it results in a proliferation of unhealthy, twiggy growth. Check azaleas for wilting or dead branches in late summer that may be the result of fungal cankers. These branches should be pruned back to clean white wood that is not infected while the weather is dry to prevent the spread of diseases. Old azaleas that have grown too large for their space in your garden can be brought down in size by cutting the large branches back severely. New growth will spring from the stubs that are left.